Fit-Body Secrets: Hormones

From what’s in our food to the fabrics of our fitness gear, the modern athlete wants transparency—and when it comes to your workout, it’s no different: We want to know what’s going on beneath the skin.

So when a recent study identified an exercise hormone called irisin—which could have implications for weight loss and fat burn—it turned heads. “Irisin is supposed to be almost magical,” explains Keith Baar, Ph.D., an associate professor at the UC Davis School of Medicine. Some say it can turn white fat—used as an energy store—into brown fat (which produces heat and burns calories), Baar explains.

Even though irisin’s effects in response to exercise continue to be investigated, when you exercise, you change not just a single molecule, but the entire soup that your body is bathed in, says Baar. Levels of testosterone, growth hormone, cortisol, and other hormones ebb and flow.

And you don’t need a Ph.D. to maximize your chemical response to exercise. Simple adjustments (inside and out of the gym) can help you burn fat, boost metabolism, and more. Start here:

Work out hungry

Growth hormone—which helps create new muscle tissue—rises with endurance exercise, but if you’re drinking a sports drink, levels don’t rise at all, says Baar. That’s because during fasted exercise, your body senses a state of stress and needs fuel. Growth hormone can increase how much fat you burn, says Baar. This means more lean tissue and better blood sugar management, too. (It’s just one of 5 reasons to skip breakfast.)

Do what you love (most of the time)

Variety is essential to results, so while you can't do one thing and one thing only, prioritizing your exercise preferences has actual payoff. When you think of cannabinoids, you may think of marijuana—but your body produces its own version of the chemicals, too, called endocannabinoids. The ‘runner’s high’ in part, is an endocannabinoid response. And to get the biggest feel-good response, you should be doing exercise you love — that's because there’s a direct relationship between how much you like to exercise and how many endocannabinoids you produce, says Baar.

If you’re running, working harder can have a positive effect on growth hormone, too, says Kraemer. High-intensity interval training works great as it puts stress on your body in a short amount of time. Multiple tissues get signals to improve oxygen uptake, upping cardio fitness levels in less time, says Kraemer.

Never, ever neglect recovery

A bigger hormonal response can certainly be good — after all, the harder you work, the more hormones your body releases, which can help you build muscle and strength. But too much of anything can be harmful, says Kraemer. Constantly overworking your body can overload your body with hormones that can do more harm than good. Take the stress hormone cortisol: it can be helpful for muscle repair post-workout (when released in moderate doses), but in high levels, it could reduce muscle growth, Kraemer says. The simple fix: rest days and recovery. Work your body hard and allow it the time it needs to re-boot.